Spatially compounding flood-nocturnal heat events over adjacent regions in the Northern Hemisphere

Compound events have become more frequent and diverse under global warming. This study specifically focuses on a type of compound events termed spatially compounding flood-nocturnal heat events over adjacent regions. Five flood hotspots are identified to compound with adjacent nocturnal heat. The flood and nocturnal heat are linked via a water vapor transport belt, with flood over the region of prominent water vapor convergence and ascending anomalies and nocturnal heat over the extension region with moderately increased humidity and weak vertical motion anomaly. The compound events for all the hotspots occur more frequently recently, with commonly positive contribution from the increasing trends of nocturnal temperature (TN) but various contribution from the trends of precipitation (Pr) and Pr-TN correlation. The positive contribution of enhanced Pr-TN correlation results from the enhanced variability of the circulation accompanied with water vapor transport. This study highlights the influence of atmospheric circulation variability on compound events.